1. Field of the Invention
The present invention relates generally to electronic packaging, and more particularly to water and weather proof packaging having multiple emitters.
2. Description of the Related Art
Light emitting diodes (LEDs) are solid state devices that convert electric energy to light, and generally comprise one or more active layers of semiconductor material sandwiched between oppositely doped layers. When a bias is applied across the doped layers, holes and electrons are injected into the active layer where they recombine to generate light. Light is emitted from the active layer and from all surfaces of the LED.
In recent years, there have been dramatic improvements in LED technology such that LEDs with increased brightness and color fidelity, smaller footprints, and overall improved emitting efficiency have been introduced. LEDs also have an increased operation lifetime compared to other emitters. For example, the operational lifetime of an LED can be over 50,000 hours, while the operational lifetime of an incandescent bulb is approximately 2,000 hours. LEDs can also be more robust than other light sources while consuming less power. For these and other reasons, LEDs are becoming more popular and are now being used in more and more applications that have traditionally been the realm of incandescent, fluorescent, halogen and other emitters.
Due at least in part to these improved LEDs and improved image processing technology, LEDs can be used as the light source for a variety of display types. In order to use LED chips in these types of applications, it is known in the art to enclose one or more LED chips in a package to provide environmental and/or mechanical protection, color selection, light focusing and the like. An LED package also includes electrical leads, contacts or traces for electrically connecting the LED package to an external circuit. The LED packages are commonly mounted on a printed circuit board (PCB).
Different LED packages can be used as the light source for indoor or outdoor displays of varying sizes, and are expected to withstand a variety of environmental conditions. These LED-based displays can comprise thousands of “pixels” or “pixel modules”, each of which can contain a plurality of LEDs. The pixel modules can use high efficiency and high brightness LEDs that allow the displays to be visible from various distances and in a variety of environmental lighting conditions. The pixel modules can have as few as three or four LEDs that allow the pixel to emit many different colors of light from combinations of red, green, blue, and/or sometimes yellow light.
Most conventional LED based displays are controlled by a computer system that accepts an incoming signal (e.g. TV signal), and based on the particular color needed at the pixel module to form the overall display image, the computer system determines which LED(s) in each of the pixel modules is to emit light and how brightly. Conductors are provided to apply the appropriate power signal to each of the LEDs in the pixel modules. A power system can also be included that provides power to each of the pixel modules; the power to each of the LEDs can be modulated so light is emitted at the desired brightness. The pixel modules can have as few as three or four LEDs that allow the pixel to emit many different colors of light from combinations of red, green, blue, and/or sometimes yellow light.
LED-based displays are becoming more common in outdoor applications and/or other locations with possible extreme environmental conditions. As their popularity increases, it is important for LED packages incorporated into such displays to withstand potentially harsh environmental conditions and water infiltration. The packages are expected to maintain their structural integrity during manufacture and use, but the integrity of such packages can become compromised.
For example, current packages in the art can experience separation between the package casing and the leads/lead frame. Such separation can allow environmental contaminants such as water and dirt to enter the package, and can reduce the overall life of the package. Furthermore, the package structures can become compromised during manufacture and use. For example, the wire bonds may become detached from the chip carrier pads and connection pads and/or may break.